Silver Ecstasy
Member
- :
- 11 MS3 Sport
So I did some testing and had some thoughts today with my Forge BPV.
But, i'd first like to explain what I understand to be true before I put those understandings into reasoning:
The stock BPV is meant to allow the appropriate amount of compromise between Vacuum and Boost. Besides the fact the stock BPV can/will leak, the stock bpv will allow for a safe amount of Vacuum. I understand that Vacuum is a good thing to have and with this situation, the more the merrier because you're allowing air to recycle and recirculate to the intake whenever you are basically NOT running Full Throttle/WOT/or running hard (for those technical people who will say our cars don't run 100% throttle.)
My understanding is, you'll want to have the same or more similar amounts of Vacuum so that you arn't overworking your turbo on lower load amounts for no reason, nor do you want to keep the BPV closed more often than it's should be, since that's basically what's happening when you have less Vacuum.
OKAY, so here's what I did:
I can't honestly say I remember what Boost #'s I seen with the stock valve, as I didn't ever really pay attention, but I will say I did notice -20 to -22 in Vacuum. I installed the Forge BPV recently with a blue spring and 2 shims. This instantly changed my throttle response to a much more aggressive tone. Power came on more violently at first, but the car didn't not pull any harder or faster. Depending on the gearing or the temperatures, i'd regularly see 14-15psi, but my Vacuum #'s were less. OFF throttle, i'd have plenty of vacuum, but during part throttle cruising, I actually had less Vacuum. Anywhere from -14 to -10 Vacuum in similar speeds. This concerned me because I also noticed that the valve would release at part throttle but it would shudder if I was starting to ease off from hard throttle. It would almost hesitate or not want to release pressure at all unless I was lifting OFF throttle completely. Boost was ON/OFF/ON/OFF instant like a light switch but I still did not notice as much Vacuum in normal driving or cruising like I did stock. SO, power would come quicker, but it wouldn't pull any better than stock as the turbo's already spinning to it's max. At this point, all I can do is wind out the rpms.
I finally decided to switch to Yellow + 2 shims today. The car drove completely different! It was definitely less violent, no shuddering between part throttle to little throttle after a hard push on the gas. And my boost #'s were still 15-16psi averages. What I also noticed was the turbo lag was more noticable (still seems completely acceptable and perfectly safe and normal). The car would take a second to build boost but when it did, it would lurch forward in that "stock" type of thrill I enjoyed experiencing when I first got the car. Vacuum #'s were absolutely acceptable and back to stock, and the car felt great to drive. I will say however, the trade-off has been more throttle required to leave from a stop. Makes sense, considering the Blue + 2 was closing quicker and wanting to build boost faster to assist the engine.
Ultimately, I can't decide which is better or safer. Having a wild child, aggressive spring setup is awesome because of it's Instant-On/OFF response. It doesn't build bigger boost, but it builds boost harder, sooner and much sooner. What I can't translate is whether I need or want turbo assistance for every instance of driving. Technically, the turbo is supposed to be compressing air into the engine during WOT/hard throttle. Utilizing the turbo for so many situations seems like an easy cause to strain and cause damage.
Then again, the yellow spring seems to react no different than stock other than it's capable of holding boost more consistently (although when I drove tonight when it was 10* colder, I wasn't seeing 15psi anymore). So...those are my thoughts. I appreciate any helpful contributions to this thread from much more knowledgable turbo guys!
But, i'd first like to explain what I understand to be true before I put those understandings into reasoning:
The stock BPV is meant to allow the appropriate amount of compromise between Vacuum and Boost. Besides the fact the stock BPV can/will leak, the stock bpv will allow for a safe amount of Vacuum. I understand that Vacuum is a good thing to have and with this situation, the more the merrier because you're allowing air to recycle and recirculate to the intake whenever you are basically NOT running Full Throttle/WOT/or running hard (for those technical people who will say our cars don't run 100% throttle.)
My understanding is, you'll want to have the same or more similar amounts of Vacuum so that you arn't overworking your turbo on lower load amounts for no reason, nor do you want to keep the BPV closed more often than it's should be, since that's basically what's happening when you have less Vacuum.
OKAY, so here's what I did:
I can't honestly say I remember what Boost #'s I seen with the stock valve, as I didn't ever really pay attention, but I will say I did notice -20 to -22 in Vacuum. I installed the Forge BPV recently with a blue spring and 2 shims. This instantly changed my throttle response to a much more aggressive tone. Power came on more violently at first, but the car didn't not pull any harder or faster. Depending on the gearing or the temperatures, i'd regularly see 14-15psi, but my Vacuum #'s were less. OFF throttle, i'd have plenty of vacuum, but during part throttle cruising, I actually had less Vacuum. Anywhere from -14 to -10 Vacuum in similar speeds. This concerned me because I also noticed that the valve would release at part throttle but it would shudder if I was starting to ease off from hard throttle. It would almost hesitate or not want to release pressure at all unless I was lifting OFF throttle completely. Boost was ON/OFF/ON/OFF instant like a light switch but I still did not notice as much Vacuum in normal driving or cruising like I did stock. SO, power would come quicker, but it wouldn't pull any better than stock as the turbo's already spinning to it's max. At this point, all I can do is wind out the rpms.
I finally decided to switch to Yellow + 2 shims today. The car drove completely different! It was definitely less violent, no shuddering between part throttle to little throttle after a hard push on the gas. And my boost #'s were still 15-16psi averages. What I also noticed was the turbo lag was more noticable (still seems completely acceptable and perfectly safe and normal). The car would take a second to build boost but when it did, it would lurch forward in that "stock" type of thrill I enjoyed experiencing when I first got the car. Vacuum #'s were absolutely acceptable and back to stock, and the car felt great to drive. I will say however, the trade-off has been more throttle required to leave from a stop. Makes sense, considering the Blue + 2 was closing quicker and wanting to build boost faster to assist the engine.
Ultimately, I can't decide which is better or safer. Having a wild child, aggressive spring setup is awesome because of it's Instant-On/OFF response. It doesn't build bigger boost, but it builds boost harder, sooner and much sooner. What I can't translate is whether I need or want turbo assistance for every instance of driving. Technically, the turbo is supposed to be compressing air into the engine during WOT/hard throttle. Utilizing the turbo for so many situations seems like an easy cause to strain and cause damage.
Then again, the yellow spring seems to react no different than stock other than it's capable of holding boost more consistently (although when I drove tonight when it was 10* colder, I wasn't seeing 15psi anymore). So...those are my thoughts. I appreciate any helpful contributions to this thread from much more knowledgable turbo guys!
